A large fraction of yield losses in wafer fabrication or processing of semiconductor devices is attributed to contamination. Contaminants can be organic or inorganic particles, films or molecular compounds, ionic materials, or atomic species. Particularly problematic, however, is contamination from abrasive particles used during processing, such as planarization. For example, during chemical mechanical planarization or polishing (CMP), a rotating substrate of semiconductor material is held against a wetted planarization or polishing surface using a liquid slurry under controlled pressure and temperature conditions. The liquid typically consists of an abrasive component, such as alumina, silica, or similar particulates, although, alternatively, a pad could include the abrasive component. Once the planarization or polishing is complete, abrasive particles typically remain on the surface of the substrate.
Thus, the primary contaminants that need to be removed from the substrate surface during/after processing, such as planarization or polishing, and prior to subsequent processing steps are alumina, silica, and oxides. Other contaminants that can also be problematic include ionic, atomic, or molecular species containing sodium, potassium, lithium, calcium, boron, manganese, sodium, titanium, zirconium, magnesium, iron, copper, nickel, gold, silicon, and aluminum. Such contaminants may diffuse into the surface of the substrate and down fracture paths.
Also, the presence of contaminants during substrate processing has become particularly problematic in high density, large scale integration (LSI) technology. For example, contaminants can cause a device to fail by improperly defining features within the integrated circuit, creating unpredictable surface topography, inducing leakage currents through insulating layers, or accelerating device wearout.
SC-1 wet cleaning solutions (mixtures of NH.sub.4 OH, H.sub.2 O.sub.2, and H.sub.2 O in a volume ratio of 1:1:5 typically) used in an "RCA clean" are commonly used to clean wafer surfaces during processing. "RCA clean" has been the primary cleaning process for the semiconductor industry for nearly 30 years. RCA cleans reportedly remove particles and organic contaminants on semiconductor surfaces without significantly attacking the semiconductor surface. RCA cleans commonly include a series of two baths (with a third optional bath) for immersion of the wafers. The first bath typically contains the basic SC-1 wet cleaning solution. The second bath is optional and typically contains hydrofluoric acid (HF) or buffered HF for removal of oxides formed from the H.sub.2 O.sub.2 in the SC-1 wet cleaning solution. Finally, the third bath is called an SC-2 wet cleaning solution, typically containing an acidic halogen solution (e.g., HCl along with H.sub.2 O.sub.2 and H.sub.2 O in a volume ratio of 1:1:6 typically) for removing heavy alkali ions and cations from the wafer surface. After immersion in each bath, the wafer surfaces are commonly rinsed in deionized water and optionally dried.
One problem associated with using such wet cleaning solution baths is that the chemicals need to be replenished frequently due to their reaction with particulates on the wafer surfaces and evaporation into the atmosphere. This is both costly and time-consuming. Recently, tetramethylammonium hydroxide (TMAH) has been utilized in wet cleaning solutions. TMAH has been shown to reduce chemical consumption, and, thus, lengthen the bath life. TMAH is reported to lengthen the bath life because it is not as readily evaporated from a standard wet cleaning solution as is ammonia in an SC-1 wet cleaning solution.
It has also been reported that phosphonic acid chelating agents added to an SC-1 wet cleaning solution reduce certain metallic contamination deposition on a silicon substrate. This conclusion was reached in the article entitled "Thin-Oxide Dielectric Strength Improvement by Adding a Phosphonic Acid Chelating Agent into NH.sub.4 OH--H.sub.2 O.sub.2 Solution" by Akiya et al., J Electrochem. Soc., Vol. 141, No. Oct. 10, 1994.
Also, it has been demonstrated that water soluble multidentate chelating agents, particularly water soluble bidentate ionic chelating agents, such as 1,2-ethylenediphosphonic acid (EDP), can be used during planarization processing to remove metal ion contaminants, as disclosed in U.S. patent application Ser. No. 08/682,308, filed on Jul. 17, 1996, entitled "A Planarization Fluid Composition Including Chelating Agents and Planarization Method Using Same."
The JTB-100 wet cleaning solution in a "Baker Clean" has also been used as a replacement for the RCA clean, as described by Cady et al. in "RCA Clean Replacement," J. Electrochem. Soc., Vol. 143, No. 6 (June 1996). In this wet cleaning solution, TMAH-based alkaline material has been used in conjunction with a carboxylate buffer to remove particulate contaminants from wafer surfaces. This cleaning solution was sprayed on wafer surfaces, followed by a rinse in deionized water. The JTB-100 wet cleaning solution replaced the SC-1 and SC-2 wet cleaning solution baths in a conventional RCA clean. An optional bath containing a solution of H.sub.2 SO.sub.4 /H.sub.2 O.sub.2 /H.sub.2 O in a volumetric ratio of 4:0.2:0.8 and an optional bath containing HF or buffered HF were used prior to the JTB-100 wet cleaning solution.
Another problem that has not been adequately addressed is the cleaning of the planarization or polishing surface both during and after processing. When planarization or polishing surfaces are used with abrasive slurries, it is important to prevent the buildup of abrasive particulates and other contaminants on such polishing surfaces. When abrasive pads are used, it is important to prevent the buildup of metal and metalloid ions and oxides, for example, on such abrasive pads. Such contaminants shorten the effective lifetime of processing equipment and should be removed to ensure precise processing of substrates during planarization or polishing without excessive contamination of the substrates.
Thus, compositions and methods are still needed to reduce, for example, the amount of metal and metalloid ion and abrasive particulate contamination of, for example, the substrate being processed and the processing equipment used. The present invention as described below provides such compositions and methods.